2-thio-1,3,4-oxadiazoles azetidine derivatives as sphingosine-1 phosphate receptors modulators

ABSTRACT

The present invention relates to 2-thio-1,3,4-oxadiazoles azetidine derivatives, processes for preparing them, pharmaceutical compositions containing them and their use as pharmaceuticals as modulators of sphingosine-1-phosphate receptors.

RELATED APPLICATION

This application claims the benefit of U.S. Provisional PatentApplication Ser. No. 61/726,206 filed Nov. 14, 2012, the disclosure ofwhich is hereby incorporated in its entirety herein by reference.

FIELD OF THE INVENTION

The present invention relates to 2-thio-1,3,4-oxadiazoles azetidinederivatives, processes for preparing them, pharmaceutical compositionscontaining them and their use as pharmaceuticals as modulators ofsphingosine-1-phosphate receptors. The invention relates specifically tothe use of these compounds and their pharmaceutical compositions totreat disorders associated with sphingosine-1-phosphate (S1P) receptormodulation.

BACKGROUND OF THE INVENTION

Sphingosine-1 phosphate is stored in relatively high concentrations inhuman platelets, which lack the enzymes responsible for its catabolism,and it is released into the blood stream upon activation ofphysiological stimuli, such as growth factors, cytokines, and receptoragonists and antigens. It may also have a critical role in plateletaggregation and thrombosis and could aggravate cardiovascular diseases.On the other hand the relatively high concentration of the metabolite inhigh-density lipoproteins (HDL) may have beneficial implications foratherogenesis. For example, there are recent suggestions thatsphingosine-1-phosphate, together with other lysolipids such assphingosylphosphorylcholine and lysosulfatide, are responsible for thebeneficial clinical effects of HDL by stimulating the production of thepotent antiatherogenic signaling molecule nitric oxide by the vascularendothelium. In addition, like lysophosphatidic acid, it is a marker forcertain types of cancer, and there is evidence that its role in celldivision or proliferation may have an influence on the development ofcancers. These are currently topics that are attracting great interestamongst medical researchers, and the potential for therapeuticintervention in sphingosine-1-phosphate metabolism is under activeinvestigation.

SUMMARY OF THE INVENTION

We have now discovered a group of novel compounds which are potent andselective sphingosine-1-phosphate modulators. As such, the compoundsdescribed herein are useful in treating a wide variety of disordersassociated with modulation of sphingosine-1-phosphate receptors. Theterm “modulator” as used herein, includes but is not limited to:receptor agonist, antagonist, inverse agonist, inverse antagonist,partial agonist, partial antagonist.

This invention describes compounds of Formula I, which havesphingosine-1-phosphate receptor biological activity. The compounds inaccordance with the present invention are thus of use in medicine, forexample in the treatment of humans with diseases and conditions that arealleviated by S1P modulation.

In one aspect, the invention provides a compound having Formula I or apharmaceutically acceptable salt thereof or stereoisomeric formsthereof, enantiomers, diastereoisomers, tautomers, zwitterions andpharmaceutically acceptable salts thereof:

wherein:

X is S, SO or SO₂;

R¹ is hydrogen, halogen, substituted or unsubstituted C₁₋₃ alkyl, CN,NO₂, C(O)R¹² or OR¹¹;R² is hydrogen, halogen, substituted or unsubstituted C₁₋₃ alkyl, CN,NO₂, C(O)R¹² or OR¹¹;R³ is hydrogen, halogen, substituted or unsubstituted C₁₋₃ alkyl, CN,NO₂, C(O)R¹² or OR¹¹;R⁴ is hydrogen, halogen, substituted or unsubstituted C₁₋₃ alkyl, CN,NO₂, C(O)R¹² or OR¹¹;R⁵ is hydrogen, halogen, substituted or unsubstituted C₁₋₃ alkyl, CN,NO₂, C(O)R¹² or OR¹¹;R⁶ is H, halogen, —OC₁₋₃ alkyl, substituted or unsubstituted C₁₋₃ alkyl;R⁷ is hydrogen, halogen, substituted or unsubstituted C₁₋₃ alkyl, CN,NO₂, C(O)R¹² or OR¹¹;

R⁸ is CH, S, O, N, NH or CH₂; R⁹ is CH, N or CH₂;

R¹⁰ is hydrogen, halogen, substituted or unsubstituted C₁₋₃ alkyl, CN,NO₂, C(O)R¹² or OR¹¹;a is 0 or 1;b is 1, 2 or 3;R¹¹ is H or C₁₋₃ alkyl;R¹² is OH or C₁₋₃ alkyl;when a is 1 then

is

when a is 0 then

and R⁸ is S, O, NH or CH₂.

In another aspect, the invention provides a compound of Formula I,wherein:

X is S;

R¹ is hydrogen, halogen, substituted or unsubstituted C₁₋₃ alkyl, CN,NO₂, C(O)R¹² or OR¹¹;R² is hydrogen, halogen, substituted or unsubstituted C₁₋₃ alkyl, CN,NO₂, C(O)R¹² or OR¹¹;R³ is hydrogen, halogen, substituted or unsubstituted C₁₋₃ alkyl, CN,NO₂, C(O)R¹² or OR¹¹;R⁴ is hydrogen, halogen, substituted or unsubstituted C₁₋₃ alkyl, CN,NO₂, C(O)R¹² or OR¹¹;R⁵ is hydrogen, halogen, substituted or unsubstituted C₁₋₃ alkyl, CN,NO₂, C(O)R¹² or OR¹¹;R⁶ is H, halogen, —OC₁₋₃ alkyl, substituted or unsubstituted C₁₋₃ alkyl;R⁷ is hydrogen, halogen, substituted or unsubstituted C₁₋₃ alkyl, CN,NO₂, C(O)R¹² or OR¹¹;

R⁸ is CH; R⁹ is CH;

R¹⁰ is hydrogen, halogen, substituted or unsubstituted C₁₋₃ alkyl, CN,NO₂, C(O)R¹² or OR¹¹;a is 1;b is 13;R¹¹ is H or C₁₋₃ alkyl;R¹² is OH or C₁₋₃ alkyl; and

The term “alkyl”, as used herein, refers to saturated, monovalent ordivalent hydrocarbon moieties having linear or branched moieties orcombinations thereof and containing 1 to 6 carbon atoms. One methylene(—CH₂—) group, of the alkyl can be replaced by oxygen, sulfur,sulfoxide, nitrogen, carbonyl, carboxyl, sulfonyl, or by a divalent C₃₋₆cycloalkyl. Alkyl groups can be substituted by halogen, hydroxyl,cycloalkyl, amino, non-aromatic heterocycles, carboxylic acid,phosphonic acid groups, sulphonic acid groups, phosphoric acid.

The term “cycloalkyl”, as used herein, refers to a monovalent ordivalent group of 3 to 8 carbon atoms, preferably 3 to 5 carbon atomsderived from a saturated cyclic hydrocarbon. Cycloalkyl groups can bemonocyclic or polycyclic. Cycloalkyl can be substituted by 1 to 3C₁₋₃alkyl groups or 1 or 2 halogens.

The term “cycloalkenyl”, as used herein, refers to a monovalent ordivalent group of 3 to 8 carbon atoms, preferably 3 to 6 carbon atomsderived from a saturated cycloalkyl having one double bond. Cycloalkenylgroups can be monocyclic or polycyclic. Cycloalkenyl groups can besubstituted by 1 to 3C₁₋₃ alkyl groups or 1 or 2 halogens.

The term “halogen”, as used herein, refers to an atom of chlorine,bromine, fluorine, iodine.

The term “alkenyl”, as used herein, refers to a monovalent or divalenthydrocarbon radical having 2 to 6 carbon atoms, derived from a saturatedalkyl, having at least one double bond. C₂₋₆ alkenyl can be in the E orZ configuration. Alkenyl groups can be substituted by 1 to 2C₁₋₃ alkyl.

The term “alkynyl”, as used herein, refers to a monovalent or divalenthydrocarbon radical having 2 to 6 carbon atoms, derived from a saturatedalkyl, having at least one triple bond.

The term “heterocycle” as used herein, refers to a 3 to 10 memberedring, which can be aromatic or non-aromatic, saturated or non-saturated,containing at least one heteroatom selected form O or N or S orcombinations of at least two thereof, interrupting the carbocyclic ringstructure. The heterocyclic ring can be saturated or non-saturated. Theheterocyclic ring can be interrupted by a C═O; the S heteroatom can beoxidized. Heterocycles can be monocyclic or polycyclic. Heterocyclicring moieties can be substituted by hydroxyl, 1 to 2C₁₋₃ alkyl or 1 to 2halogens. Usually, in the present case, heterocyclic groups are 5 or 6membered rings. Usually, in the present case, heterocyclic groups arepyridine, furan, azetidine, thiazol, thiophene, oxazol, pyrazol.

The term “aryl” as used herein, refers to an organic moiety derived froman aromatic hydrocarbon consisting of a ring containing 6 to 10 carbonatoms by removal of one hydrogen, which can be substituted by 1 to 3halogen atoms or by 1 to 2C₁₋₃ alkyl groups. Usually aryl is phenyl.Preferred substitution site on phenyl are meta and para positions.

The term “hydroxyl” as used herein, represents a group of formula “—OH”.

The term “carbonyl” as used herein, represents a group of formula“—C(O)”.

The term “carboxyl” as used herein, represents a group of formula“—C(O)O—”.

The term “sulfonyl” as used herein, represents a group of formula“—SO₂”.

The term “sulfate” as used herein, represents a group of formula“—O—S(O)₂—O—”.

The term “carboxylic acid” as used herein, represents a group of formula“—C(O)OH”.

The term “sulfoxide” as used herein, represents a group of formula“—S═O”. The term “phosphonic acid” as used herein, represents a group offormula “—P(O)(OH)₂”.

The term “phosphoric acid” as used herein, represents a group of formula“—(O)P(O)(OH)₂”.

The term “boronic acid”, as used herein, represents a group of formula“—B(OH)₂”.

The term “sulphonic acid” as used herein, represents a group of formula“—S(O)₂OH”.

The formula “H”, as used herein, represents a hydrogen atom.

The formula “O”, as used herein, represents an oxygen atom.

The formula “N”, as used herein, represents a nitrogen atom.

The formula “S”, as used herein, represents a sulfur atom.

Some compounds of the invention are:

-   1-[3-Methyl-4-(5-{[1-(3-nitrophenyl)propyl]thio}-1,3,4-oxadiazol-2-yl)benzyl]azetidine-3-carboxylic    acid;-   1-[3-Methyl-4-(5-{[1-(3-nitrophenyl)ethyl]thio}-1,3,4-oxadiazol-2-yl)benzyl]azetidine-3-carboxylic    acid;-   1-(4-{5-[(3-Chloro-2-fluorobenzyl)sulfanyl]-1,3,4-oxadiazol-2-yl}benzyl)azetidine-3-carboxylic    acid;-   1-(4-{5-[(1-Phenylbutyl)    sulfanyl]-1,3,4-oxadiazol-2-yl}benzyl)azetidine-3-carboxylic acid.

Some compounds of Formula I and some of their intermediates have atleast one stereogenic center in their structure. This stereogenic centermay be present in an R or S configuration, said R and S notation is usedin correspondence with the rules described in Pure Appli. Chem. (1976),45, 11-13.

The term “pharmaceutically acceptable salts” refers to salts orcomplexes that retain the desired biological activity of the aboveidentified compounds and exhibit minimal or no undesired toxicologicaleffects. The “pharmaceutically acceptable salts” according to theinvention include therapeutically active, non-toxic base or acid saltforms, which the compounds of Formula I are able to form.

The acid addition salt form of a compound of Formula I that occurs inits free form as a base can be obtained by treating the free base withan appropriate acid such as an inorganic acid, such as for example,hydrochloric acid, hydrobromic acid, sulfuric acid, phosphoric acid,nitric acid and the like; or an organic acid such as for example,acetic, hydroxyacetic, propanoic, lactic, pyruvic, malonic, fumaricacid, maleic acid, oxalic acid, tartaric acid, succinic acid, malicacid, ascorbic acid, benzoic acid, tannic acid, pamoic acid, citric,methylsulfonic, ethanesulfonic, benzenesulfonic, formic and the like(Handbook of Pharmaceutical Salts, P. Heinrich Stahal& Camille G.Wermuth (Eds), Verlag Helvetica Chimica Acta—Zürich, 2002, 329-345).

The base addition salt form of a compound of Formula I that occurs inits acid form can be obtained by treating the acid with an appropriatebase such as an inorganic base, for example, sodium hydroxide, magnesiumhydroxide, potassium hydroxide, calcium hydroxide, ammonia and the like;or an organic base such as for example, L-Arginine, ethanolamine,betaine, benzathine, morpholine and the like. (Handbook ofPharmaceutical Salts, P. Heinrich Stahal& Camille G. Wermuth (Eds),Verlag Helvetica Chimica Acta—Zürich, 2002, 329-345).

Compounds according to the present invention may exist in differentpolymorphic forms. Although not explicitly indicated in the aboveformula, such forms are intended to be included within the scope of thepresent invention.

The compounds of the invention are indicated for use in treating orpreventing conditions in which there is likely to be a componentinvolving the sphingosine-1-phosphate receptors.

In another embodiment, there are provided pharmaceutical compositionsincluding at least one compound of the invention in a pharmaceuticallyacceptable carrier.

In a further embodiment of the invention, there are provided methods fortreating disorders associated with modulation of sphingosine-1-phosphatereceptors. Such methods can be performed, for example, by administeringto a subject in need thereof a pharmaceutical composition containing atherapeutically effective amount of at least one compound of theinvention.

These compounds are useful for the treatment of mammals, includinghumans, with a range of conditions and diseases that are alleviated byS1P modulation: not limited to the treatment of diabetic retinopathy,other retinal degenerative conditions, dry eye, angiogenesis and wounds.

Therapeutic utilities of S1P modulators are ocular diseases, such as butnot limited to: wet and dry age-related macular degeneration, diabeticretinopathy, angiogenesis inhibition, retinopathy of prematurity,retinal edema, geographic atrophy, glaucomatous optic neuropathy,chorioretinopathy, hypertensive retinopathy, ocular ischemic syndrome,prevention of inflammation-induced fibrosis in the back of the eye,various ocular inflammatory diseases including uveitis, scleritis,keratitis, and retinal vasculitis; or systemic vascular barrier relateddiseases such as but not limited to: various inflammatory diseases,including acute lung injury, its prevention, sepsis, tumor metastasis,atherosclerosis, pulmonary edemas, and ventilation-induced lung injury;or autoimmune diseases and immunosuppression such as but not limited to:rheumatoid arthritis, Crohn's disease, Graves' disease, inflammatorybowel disease, multiple sclerosis, Myasthenia gravis, Psoriasis,ulcerative colitis, autoimmune uveitis, renal ischemia/perfusion injury,contact hypersensitivity, atopic dermititis, and organ transplantation;or allergies and other inflammatory diseases such as but not limited to:urticaria, bronchial asthma, and other airway inflammations includingpulmonary emphysema and chronic obstructive pulmonary diseases; orcardiac protection such as but not limited to: ischemia reperfusioninjury and atherosclerosis; or wound healing such as but not limited to:scar-free healing of wounds from cosmetic skin surgery, ocular surgery,GI surgery, general surgery, oral injuries, various mechanical, heat andburn injuries, prevention and treatment of photoaging and skin ageing,and prevention of radiation-induced injuries; or bone formation such asbut not limited to: treatment of osteoporosis and various bone fracturesincluding hip and ankles; or anti-nociceptive activity such as but notlimited to: visceral pain, pain associated with diabetic neuropathy,rheumatoid arthritis, chronic knee and joint pain, tendonitis,osteoarthritis, neuropathic pains; or central nervous system neuronalactivity in Alzheimer's disease, age-related neuronal injuries; or inorgan transplant such as renal, corneal, cardiac or adipose tissuetransplant.

In still another embodiment of the invention, there are provided methodsfor treating disorders associated with modulation ofsphingosine-1-phosphate receptors. Such methods can be performed, forexample, by administering to a subject in need thereof a therapeuticallyeffective amount of at least one compound of the invention, or anycombination thereof, or pharmaceutically acceptable salts, individualenantiomers, and diastereomers thereof.

The present invention concerns the use of a compound of Formula I orFormula II or a pharmaceutically acceptable salt thereof, for themanufacture of a medicament for the treatment of ocular disease, wet anddry age-related macular degeneration, diabetic retinopathy, retinopathyof prematurity, retinal edema, geographic atrophy, angiogenesisinhibition, glaucomatous optic neuropathy, chorioretinopathy,hypertensive retinopathy, ocular ischemic syndrome, prevention ofinflammation-induced fibrosis in the back of the eye, various ocularinflammatory diseases including uveitis, scleritis, keratitis, andretinal vasculitis; or systemic vascular barrier related diseases,various inflammatory diseases, including acute lung injury, itsprevention, sepsis, tumor metastasis, atherosclerosis, pulmonary edemas,and ventilation-induced lung injury; or autoimmune diseases andimmunosuppression, rheumatoid arthritis, Crohn's disease, Graves'disease, inflammatory bowel disease, multiple sclerosis, Myastheniagravis, Psoriasis, ulcerative colitis, autoimmune uveitis, renalischemia/perfusion injury, contact hypersensitivity, atopic dermititis,and organ transplantation; or allergies and other inflammatory diseases,urticaria, bronchial asthma, and other airway inflammations includingpulmonary emphysema and chronic obstructive pulmonary diseases; orcardiac protection, ischemia reperfusion injury and atherosclerosis; orwound healing, scar-free healing of wounds from cosmetic skin surgery,ocular surgery, GI surgery, general surgery, oral injuries, variousmechanical, heat and burn injuries, prevention and treatment ofphotoaging and skin ageing, and prevention of radiation-inducedinjuries; or bone formation, treatment of osteoporosis and various bonefractures including hip and ankles; or anti-nociceptive activity,visceral pain, pain associated with diabetic neuropathy, rheumatoidarthritis, chronic knee and joint pain, tendonitis, osteoarthritis,neuropathic pains; or central nervous system neuronal activity inAlzheimer's disease, age-related neuronal injuries; or in organtransplant such as renal, corneal, cardiac or adipose tissue transplant.

The actual amount of the compound to be administered in any given casewill be determined by a physician taking into account the relevantcircumstances, such as the severity of the condition, the age and weightof the patient, the patient's general physical condition, the cause ofthe condition, and the route of administration.

The patient will be administered the compound orally in any acceptableform, such as a tablet, liquid, capsule, powder and the like, or otherroutes may be desirable or necessary, particularly if the patientsuffers from nausea. Such other routes may include, without exception,transdermal, parenteral, subcutaneous, intranasal, via an implant stent,intrathecal, intravitreal, topical to the eye, back to the eye,intramuscular, intravenous, and intrarectal modes of delivery.Additionally, the formulations may be designed to delay release of theactive compound over a given period of time, or to carefully control theamount of drug released at a given time during the course of therapy.

In another embodiment of the invention, there are providedpharmaceutical compositions including at least one compound of theinvention in a pharmaceutically acceptable carrier thereof. The phrase“pharmaceutically acceptable” means the carrier, diluent or excipientmust be compatible with the other ingredients of the formulation and notdeleterious to the recipient thereof.

Pharmaceutical compositions of the present invention can be used in theform of a solid, a solution, an emulsion, a dispersion, a patch, amicelle, a liposome, and the like, wherein the resulting compositioncontains one or more compounds of the present invention, as an activeingredient, in admixture with an organic or inorganic carrier orexcipient suitable for enteral or parenteral applications. Inventioncompounds may be combined, for example, with the usual non-toxic,pharmaceutically acceptable carriers for tablets, pellets, capsules,suppositories, solutions, emulsions, suspensions, and any other formsuitable for use. The carriers which can be used include glucose,lactose, gum acacia, gelatin, mannitol, starch paste, magnesiumtrisilicate, talc, corn starch, keratin, colloidal silica, potatostarch, urea, medium chain length triglycerides, dextrans, and othercarriers suitable for use in manufacturing preparations, in solid,semisolid, or liquid form. In addition auxiliary, stabilizing,thickening and coloring agents and perfumes may be used. Inventioncompounds are included in the pharmaceutical composition in an amountsufficient to produce the desired effect upon the process or diseasecondition.

Pharmaceutical compositions containing invention compounds may be in aform suitable for oral use, for example, as tablets, troches, lozenges,aqueous or oily suspensions, dispersible powders or granules, emulsions,hard or soft capsules, or syrups or elixirs. Compositions intended fororal use may be prepared according to any method known in the art forthe manufacture of pharmaceutical compositions and such compositions maycontain one or more agents selected from the group consisting of asweetening agent such as sucrose, lactose, or saccharin, flavoringagents such as peppermint, oil of wintergreen or cherry, coloring agentsand preserving agents in order to provide pharmaceutically elegant andpalatable preparations. Tablets containing invention compounds inadmixture with non-toxic pharmaceutically acceptable excipients may alsobe manufactured by known methods. The excipients used may be, forexample, (1) inert diluents such as calcium carbonate, lactose, calciumphosphate or sodium phosphate; (2) granulating and disintegrating agentssuch as corn starch, potato starch or alginic acid; (3) binding agentssuch as gum tragacanth, corn starch, gelatin or acacia, and (4)lubricating agents such as magnesium stearate, stearic acid or talc. Thetablets may be uncoated or they may be coated by known techniques todelay disintegration and absorption in the gastrointestinal tract andthereby provide a sustained action over a longer period. For example, atime delay material such as glyceryl monostearate or glyceryl distearatemay be employed.

In some cases, formulations for oral use may be in the form of hardgelatin capsules wherein the invention compounds are mixed with an inertsolid diluent, for example, calcium carbonate, calcium phosphate orkaolin. They may also be in the form of soft gelatin capsules whereinthe invention compounds are mixed with water or an oil medium, forexample, peanut oil, liquid paraffin or olive oil.

The pharmaceutical compositions may be in the form of a sterileinjectable suspension. This suspension may be formulated according toknown methods using suitable dispersing or wetting agents and suspendingagents. The sterile injectable preparation may also be a sterileinjectable solution or suspension in a non-toxic parenterally-acceptablediluent or solvent, for example, as a solution in 1,3-butanediol.Sterile, fixed oils are conventionally employed as a solvent orsuspending medium. For this purpose any bland fixed oil may be employedincluding synthetic mono- or diglycerides, fatty acids (including oleicacid), naturally occurring vegetable oils like sesame oil, coconut oil,peanut oil, cottonseed oil, etc., or synthetic fatty vehicles like ethyloleate or the like. Buffers, preservatives, antioxidants, and the likecan be incorporated as required.

Pharmaceutical compositions containing invention compounds may be in aform suitable for topical use, for example, as oily suspensions, assolutions or suspensions in aqueous liquids or nonaqueous liquids, or asoil-in-water or water-in-oil liquid emulsions. Pharmaceuticalcompositions may be prepared by combining a therapeutically effectiveamount of at least one compound according to the present invention, or apharmaceutically acceptable salt thereof, as an active ingredient withconventional ophthalmically acceptable pharmaceutical excipients and bypreparation of unit dosage suitable for topical ocular use. Thetherapeutically efficient amount typically is between about 0.0001 andabout 5% (w/v), preferably about 0.001 to about 2.0% (w/v) in liquidformulations.

For ophthalmic application, preferably solutions are prepared using aphysiological saline solution as a major vehicle. The pH of suchophthalmic solutions should preferably be maintained between 4.5 and 8.0with an appropriate buffer system, a neutral pH being preferred but notessential. The formulations may also contain conventionalpharmaceutically acceptable preservatives, stabilizers and surfactants.Preferred preservatives that may be used in the pharmaceuticalcompositions of the present invention include, but are not limited to,benzalkonium chloride, chlorobutanol, thimerosal, phenylmercuric acetateand phenylmercuric nitrate. A preferred surfactant is, for example,Tween 80. Likewise, various preferred vehicles may be used in theophthalmic preparations of the present invention. These vehiclesinclude, but are not limited to, polyvinyl alcohol, povidone,hydroxypropyl methyl cellulose, poloxamers, carboxymethyl cellulose,hydroxyethyl cellulose cyclodextrin and purified water.

Tonicity adjustors may be added as needed or convenient. They include,but are not limited to, salts, particularly sodium chloride, potassiumchloride, mannitol and glycerin, or any other suitable ophthalmicallyacceptable tonicity adjustor.

Various buffers and means for adjusting pH may be used so long as theresulting preparation is ophthalmically acceptable. Accordingly, buffersinclude acetate buffers, citrate buffers, phosphate buffers and boratebuffers. Acids or bases may be used to adjust the pH of theseformulations as needed.

In a similar manner an ophthalmically acceptable antioxidant for use inthe present invention includes, but is not limited to, sodiummetabisulfite, sodium thiosulfate, acetylcysteine, butylatedhydroxyanisole and butylated hydroxytoluene. Other excipient componentswhich may be included in the ophthalmic preparations are chelatingagents. The preferred chelating agent is edentate disodium, althoughother chelating agents may also be used in place of or in conjunctionwith it.

The ingredients are usually used in the following amounts:

Ingredient Amount (% w/v) active ingredient about 0.001-5 preservative 0-0.10 vehicle 0-40 tonicity adjustor 1-10 buffer 0.01-10   pH adjustorq.s. pH 4.5-7.8 antioxidant as needed surfactant as needed purifiedwater to make 100%

The actual dose of the active compounds of the present invention dependson the specific compound, and on the condition to be treated; theselection of the appropriate dose is well within the knowledge of theskilled artisan.

The ophthalmic formulations of the present invention are convenientlypackaged in forms suitable for metered application, such as incontainers equipped with a dropper, to facilitate application to theeye. Containers suitable for drop wise application are usually made ofsuitable inert, non-toxic plastic material, and generally containbetween about 0.5 and about 15 ml solution. One package may contain oneor more unit doses. Especially preservative-free solutions are oftenformulated in non-resalable containers containing up to about ten,preferably up to about five units doses, where a typical unit dose isfrom one to about 8 drops, preferably one to about 3 drops. The volumeof one drop usually is about 20-35 ml.

Invention compounds may also be administered in the form ofsuppositories for rectal administration of the drug. These compositionsmay be prepared by mixing the invention compounds with a suitablenon-irritating excipient, such as cocoa butter, synthetic glycerideesters of polyethylene glycols, which are solid at ordinarytemperatures, but liquefy and/or dissolve in the rectal cavity torelease the drug.

Since individual subjects may present a wide variation in severity ofsymptoms and each drug has its unique therapeutic characteristics, theprecise mode of administration and dosage employed for each subject isleft to the discretion of the practitioner.

The compounds and pharmaceutical compositions described herein areuseful as medicaments in mammals, including humans, for treatment ofdiseases and/or alleviations of conditions which are responsive totreatment by agonists or functional antagonists ofsphingosine-1-phosphate receptors. Thus, in further embodiments of theinvention, there are provided methods for treating a disorder associatedwith modulation of sphingosine-1-phosphate receptors. Such methods canbe performed, for example, by administering to a subject in need thereofa pharmaceutical composition containing a therapeutically effectiveamount of at least one invention compound. As used herein, the term“therapeutically effective amount” means the amount of thepharmaceutical composition that will elicit the biological or medicalresponse of a subject in need thereof that is being sought by theresearcher, veterinarian, medical doctor or other clinician. In someembodiments, the subject in need thereof is a mammal. In someembodiments, the mammal is human.

The present invention concerns also processes for preparing thecompounds of Formula I. The compounds of Formula I according to theinvention can be prepared analogously to conventional methods asunderstood by the person skilled in the art of synthetic organicchemistry. Synthetic Scheme 1 set forth below, illustrates how compoundsaccording to the invention can be made.

General Procedure

To a solution of 4-hydroxylmethyl benzoic hydrazine in ethanol wereadded CS₂ and Et₃N. After heating to reflux for 16 h with stirring, thereaction mixture was diluted with ethyl acetate. The mixture was washedwith 10% HCl solution and brine, dried over magnesium sulfate, andconcentrated. Purification of the residue by MPLC (65% ethyl acetate inhexanes) the corresponding mercapto oxadiazo intermediate.

To the oxadiazol intermediate in water was added a bromoethylphenyl andsodium hudroxide. After stirring at RT for 16 h, the resultingprecipitate was collected by filtration. The solid was dissolved inacetone and purified by MPLC (60% ethyl acetate in hexanes) to affordthe corresponding methanol intermediate.

To a solution of periodic acid in acetonitrile (5 mL) which was stirredvigorously for 15 min was added the methanol intermediate at 0° C.followed by pyridinium chlorochromate (2.4 mg, 0.01 mmol). Afterstirring at 0° C. for 30 min and RT for 30 min, the reaction mixture wasdiluted with ethyl acetate. The mixture was washed with a 1:1 solutionof brine/water, saturated sodium sulfate, and brine, dried overmagnesium sulfate, and concentrated. Purification of the residue by MPLC(15% ethyl acetate in hexanes) gave the corresponding aldehydeintermediate.

To a solution of the aldehyde intermediate in methanol were added(3-aminopropyl) phosphonic acid in methanol was added3-azetidinecarboxylic acid. After the reaction mixture was stirred at RTfor 2.5 h, sodium borohydride (9 mg, 0.22 mmol) was added. The reactionmixture was stirred at RT for another 1.5 h, then concentrated andpurified by MPLC (80% methanol in ethyl acetate) to give to give thedesired compound of Formula I.

The following abbreviations are used in the examples:

MeOH methanolHCl hydrochloric acidrt or RT room temperatureCDCl₃ deuterated chloroformNH₂NH₂.H₂O hydrazineCS₂ carbon disulfideEt₃N thriethylamineEtOH ethanolNaOH sodium hydroxideLAH lithium aluminum hydrideH₅IO₆ periodic acidBu₄NOH tetrabutylammonium hydroxideCD₃OD deuterated methanolMPLC medium pressure liquid chromatographyTHF tetrahydrofuranDiBAL diisobutylaluminum hydrideNaCNBH₃ sodium borohydride

Those skilled in the art will be able to routinely modify and/or adaptthe general scheme to synthesize any compound of the invention coveredby Formula I.

DETAILED DESCRIPTION OF THE INVENTION

It is to be understood that both the foregoing general description andthe following detailed description are exemplary and explanatory onlyand are not restrictive of the invention claimed. As used herein, theuse of the singular includes the plural unless specifically statedotherwise.

It will be readily apparent to those skilled in the art that some of thecompounds of the invention may contain one or more asymmetric centers,such that the compounds may exist in enantiomeric as well as indiastereomeric forms. Unless it is specifically noted otherwise, thescope of the present invention includes all enantiomers, diastereomersand racemic mixtures. Some of the compounds of the invention may formsalts with pharmaceutically acceptable acids or bases, and suchpharmaceutically acceptable salts of the compounds described herein arealso within the scope of the invention.

The present invention includes all pharmaceutically acceptableisotopically enriched compounds. Any compound of the invention maycontain one or more isotopic atoms enriched or different than thenatural ratio such as deuterium ²H (or D) in place of protium ¹H (or H)or use of ¹³C enriched material in place of ¹²C and the like. Similarsubstitutions can be employed for N, O and S. The use of isotopes mayassist in analytical as well as therapeutic aspects of the invention.For example, use of deuterium may increase the in vivo half-life byaltering the metabolism (rate) of the compounds of the invention. Thesecompounds can be prepared in accord with the preparations described byuse of isotopically enriched reagents.

The following examples are for illustrative purposes only and are notintended, nor should they be construed as limiting the invention in anymanner. Those skilled in the art will appreciate that variations andmodifications of the following examples can be made without exceedingthe spirit or scope of the invention.

As will be evident to those skilled in the art, individual isomericforms can be obtained by separation of mixtures thereof in conventionalmanner. For example, in the case of diasteroisomeric isomers,chromatographic separation may be employed.

Compound names were generated with ACDLabs version 12.5, andintermediates and reagent names used in the examples were generated withsoftware such as Chem Bio Draw Ultra version 12.0 or Auto Nom 2000 fromMDL ISIS Draw 2.5 SP1.

In general, characterization of the compounds is performed according tothe following methods NMR spectra are recorded on 300 and/or 600 MHzVarian and acquired at room temperature. Chemical shifts are given inppm referenced either to internal TMS or to the solvent signal.

All the reagents, solvents, catalysts for which the synthesis is notdescribed are purchased from chemical vendors such as Sigma Aldrich,Fluka, Bio-Blocks, Combi-blocks, TCI, VWR, Lancaster, Oakwood, TransWorld Chemical, Alfa, Fisher, AK Scientific, AmFine Com, Carbocore,Maybridge, Frontier, Matrix, Ukrorgsynth, Toronto, Ryan Scientific,SiliCycle, Anaspec, Syn Chem, Chem-Impex, MIC-scientific, Ltd; howeversome known intermediates, were prepared according to publishedprocedures.

Usually the compounds of the invention were purified by columnchromatography (Auto-column) on an Teledyne-ISCO CombiFlash with asilica column, unless noted otherwise.

Example 1

Intermediate 1

[4(5-Mercapto-1,3,4-oxadiazol-2-yl)phenyl]methanol

To a solution of 4-(Hydroxymethyl)benzoic hydrazide CAS [58855-42-8](1.4 g, 8.4 mmol) in ethanol (14 mL) were added carbon disulfide (1.12mL, 18.5 mmol) and triethyl amine (1.3 mL, 9.3 mmol). After heating toreflux for 16 h with stirring, the reaction mixture was diluted withethyl acetate. The mixture was washed with 10% HCl solution and brine,dried over magnesium sulfate, and concentrated. Purification of theresidue by MPLC (65% ethyl acetate in hexanes) gave 1.62 g of[4-(5-Mercapto-1,3,4-oxadiazol-2-yl)phenyl]methanol as a colorlesssolid.

¹H NMR (600 MHz, CD₃OD) δ 7.90 (ddd, J=0.59, 2.05, 8.51 Hz, 2H), 7.54(d, J=7.92 Hz, 2H), 4.68 (s, 2H).

Example 2 Intermediate 2(4-{5-[(3-Chloro-2-fluorobenzyl)thio]-1,3,4-oxadiazol-2-yl}phenyl)methanol

To a solution of Intermediate 1 (596 mg, 2.86 mmol) and1-(Bromomethyl)-3-chloro-2-fluorobenzene CAS [85070-47-9] (639 mg, 2.86mmol) in water (13 mL) was added NaOH (1 M, 3.2 mL). After stirring atRT for 16 h, the resulting precipitate was collected by filtration. Thesolid was dissolved in acetone and purified by MPLC (60% ethyl acetatein hexanes) to afford 703 mg of4-{5-[(3-Chloro-2-fluorobenzyl)thio]-1,3,4-oxadiazol-2-yl}phenyl)methanolas a colorless solid.

¹H NMR (600 MHz, CDCl₃) δ 7.97 (d, J=8.22 Hz, 2H), 7.48 (s, 1H), 7.48(ddd, J=1.76, 6.16, 8.22 Hz, 1H), 7.35 (ddd, J=1.17, 6.75, 8.80 Hz, 1H),7.05 (td, J=0.88, 7.92 Hz, 1H), 4.78 (d, J=5.58 Hz, 2H), 4.54 (d, J=0.59Hz, 2H), 2.01 (t, J=5.87 Hz, 1H).

Intermediates 3, 4 and 5 were prepared from Intermediate 1, in a similarmanner to the procedure described in Example 2 for Intermediate 2. Theresults are tabulated below in Table 1.

TABLE 1 Interm. Structure No. IUPAC Name ¹H NMR δ (ppm) 3

  [4-(5-{[1-(3- Nitrophenyl)propyl]thio}- 1,3,4-oxadiazol-2-yl)phenyl]methanol ¹H NMR (300 MHz, CDCl₃) δ 8.32 (t, J = 1.90 Hz, 1H),8.13 (ddd, J = 1.17, 2.27, 8.28 Hz, 1H), 7.90-7.94 (m, 2H), 7.80 (dt, J= 1.47, 7.62 Hz, 1H), 7.45- 7.54 (m, 3H), 4.85 (dd, J = 7.03, 8.50 Hz,1H), 4.77 (d, J = 5.57 Hz, 2H), 2.06-2.33 (m, 2H), 1.98 (t, J = 5.86 Hz,1H), 1.05 (t, J = 7.33 Hz, 3H) 4

  [4-(5-{[1-(3- Nitrophenyl)ethyl]thio}- 1,3,4-oxadiazol-2-yl)phenyl]methanol ¹H NMR (300 MHz, CDCl₃) δ 8.36 (t, J = 1.90 Hz, 1H),8.13 (ddd, J = 0.90, 2.05, 8.20 Hz, 1H), 7.92 (d, J = 8.20 Hz, 2H), 7.84(d, J = 7.91 Hz, 1H), 7.53 (d, J = 7.91 Hz, 1H), 7.47 (d, J = 8.20 Hz,2H), 5.11 (q, J = 7.03 Hz, 1H), 4.77 (d, J = 5.57 Hz, 2H), 2.28 (t, J =5.86 Hz, 1H), 1.89 (d, J = 7.03 Hz, 3H) 5

  (4-{5-[(1-phenylbutyl)thio]- 1,3,4-oxadiazol-2- yl}phenyl)methanol ¹HNMR (300 MHz, CDCl₃) δ 7.90 (d, J = 8.50 Hz, 2H), 7.46 (d, J = 8.50 Hz,2H), 7.41 (dd, J = 1.76, 8.50 Hz, 2H), 7.24-7.35 (m, 3H), 4.83 (dd, J =6.45, 8.79 Hz, 1H), 4.76 (s, 2H), 1.99- 2.23 (m, 2H), 1.25-1.49 (m, 2H),0.93 (t, J = 7.33 Hz, 3H)

Example 3 Intermediate 64-{5-[(3-Chloro-2-fluorobenzyl)thio]-1,3,4-oxadiazol-2-yl}benzaldehyde

To a solution of periodic acid (137 mg, 0.6 mmol) in acetonitrile (5 mL)that was stirred vigorously for 15 min was added Intermediate 2 (200 mg,0.57 mmol) at 0° C. followed by pyridinium chlorochromate (2.4 mg, 0.01mmol). After stirring at 0° C. for 30 min and RT for 30 min, thereaction mixture was diluted with ethyl acetate. The mixture was washedwith a 1:1 solution of brine/water, saturated sodium sulfate, and brine,dried over magnesium sulfate, and concentrated. Purification of theresidue by MPLC (15% ethyl acetate in hexanes) gave rise to 149 mg of4-{5-[(3-Chloro-2-fluorobenzyl)thio]-1,3,4-oxadiazol-2-yl}benzaldehydeas a colorless solid.

¹H NMR (300 MHz, CDCl₃) δ 10.09 (s, 1H), 8.17 (d, J=8.20 Hz, 2H), 8.01(d, J=7.91 Hz, 2H), 7.49 (t, J=6.59 Hz, 1H), 7.36 (t, J=7.91 Hz, 1H),7.06 (t, J=7.76 Hz, 1H), 4.58 (s, 2H).

Intermediates 7 and 8 were prepared from the corresponding startingmaterials, in a similar manner to the procedure described in Example 3for Intermediate 6. The results are tabulated below in Table 2.

TABLE 2 Interm. Structure Interm. No. IUPAC Name No. ¹H NMR δ (ppm) 7

  4-(5-{[1-(3- Nitrophenyl)propyl]thio}- 1,3,4-oxadiazol-2-yl)benzaldehyde 3 ¹H NMR (300 MHz, CDCl₃) δ 10.08 (s, 1H), 8.32-8.36 (m,1H), 8.10-8.16 (m, 1H), 8.12 (d, J = 8.50 Hz, 1H), 7.99 (d, J = 8.50 Hz,1H), 7.94 (d, J = 8.50 Hz, 1H), 7.78-7.85 (m, 1H), 7.48-7.59 (m, 2H),4.90 (dd, J = 7.18, 8.35 Hz, 1H), 2.08- 2.36 (m, 2H), 1.06 (t, J = 7.33Hz, 3H) 8

  4-(5-{[1-(3- Nitrophenyl)ethyl]thio}- 1,3,4-oxadiazol-2-yl)benzaldehyde 4 ¹H NMR (600 MHz, CD₃OD) δ: 10.08 (s, 1H), 8.38 (t, J =1.9 Hz, 1H), 8.09-8.19 (m, 3H), 7.96- 8.05 (m, 2H), 7.87 (d, J = 7.6 Hz,1H), 7.49-7.60 (m, 1H), 5.17 (q, J = 7.1 Hz, 1H), 1.92 (d, J = 7.3 Hz,3H) 9

  4-{5-[(1-Phenylbutyl)thio]- 1,3,4-oxadiazol-2-yl} benzaldehyde 5 1HNMR (300 MHz, CDCl₃) δ 10.08 (s, 1H), 8.12 (d, J = 8.20 Hz, 2H), 7.99(d, J = 8.20 Hz, 2H), 7.43 (d, J = 6.74 Hz, 2H), 7.23-7.36 (m, 3H), 4.88(dd, J = 6.45, 9.08 Hz, 1H), 2.01-2.26 (m, 2H), 1.31-1.50 (m, 2H), 0.94(t, J = 7.33 Hz, 3H)

Example 4 Compound 11-(4-{5-[(13-Chloro-2-fluorobenzyl)thio]-1,3,4-oxadiazol-2-yl}benzyl)azetidine-3-carboxylicacid

To a solution of Intermediate 6 (51 mg, 0.15 mmol) and in methanol (5mL) was added 3-azetidinecarboxylic acid ([CAS 36476-78-5] 16 mg, 0.15mmol). After the reaction mixture was stirred at RT for 2.5 h, sodiumborohydride (9 mg, 0.22 mmol) was added. After the mixture was stirredat RT for 1.5 h, the mixture was concentrated and purified by MPLC (80%methanol in ethyl acetate) to give 17 mg of Compound 1 as a colorlesssolid.

¹H NMR (300 MHz, CD₃OD) δ 7.98 (d, J=8.50 Hz, 2H), 7.55 (d, J=8.50 Hz,2H), 7.49 (ddd, J=1.47, 6.15, 7.62 Hz, 1H), 7.42 (ddd, J=1.47, 6.74,8.20 Hz, 1H), 7.13 (td, J=1.03, 7.98 Hz, 1H), 4.59 (s, 2H), 3.97 (s,2H), 3.80 (dd, J=8.50, 9.08 Hz, 2H), 3.67 (dd, J=7.91, 9.08 Hz, 2H),3.34 (s, 1H).

Compounds 2 and 3 were prepared from the corresponding startingmaterials, in a similar manner to the procedure described in Example 4for Compound 1. The results are tabulated below in Table 3.

TABLE 3 Cmpd Structure Interm. No. IUPAC Name No. ¹H NMR δ (ppm) 2

  1-[3-Methyl-4-(5-{[1-(3- nitrophenyl)ethyl]thio}- 1,3,4-oxadiazol-2-yl)benzyl]azetidine-3- carboxylic acid 8 ¹H NMR (300 MHz, CD₃OD) δ 8.37(s, 1H), 8.14 (d, J = 8.50 Hz, 1H), 7.94 (d, J = 7.91 Hz, 1H), 7.78 (d,J = 7.91 Hz, 1H), 7.60 (t, J = 7.62 Hz, 1H), 7.39 (s, 1H), 7.35 (d, J =7.91 Hz, 1H), 5.48 (s, 1H), 5.16 (q, J = 7.33 Hz, 1H), 4.01 (s, 2H),3.87 (t, J = 8.79 Hz, 2H), 3.76 (dd, J = 7.91, 8.79 Hz, 2H), 2.58 (s,3H), 1.87 (d, J = 7.03 Hz, 3H) 3

  1-[3-Methyl-4-(5-{[1-(3- nitrophenyl)propyl]thio}- 1,3,4-oxadiazol-2-yl)benzyl]azetidine-3- carboxylic acid 7 ¹H NMR (300 MHz, CD₃OD) δ 8.34(s, 1H), 8.14 (d, J = 8.20 Hz, 1H), 7.90 (d, J = 7.62 Hz, 1H), 7.78 (d,J = 8.20 Hz, 1H), 7.60 (dd, J = 7.91, 8.79 Hz, 1H), 7.38 (s, 1H), 7.35(d, J = 7.91 Hz, 1H), 4.91 (dd, J = 7.03, 7.62 Hz, 1H), 4.00 (s, 2H),3.87 (dd, J = 8.50, 9.08 Hz, 2H), 3.75 (dd, J = 8.79, 9.38 Hz, 2H), 3.35(s, 1H), 2.57 (s, 3H), 2.10- 2.31 (m, 2H), 1.05 (t, J = 7.18 Hz, 3H) 4

  1-(4-{5-[(1-Phenylbutyl) sulfanyl]-1,3,4-oxadiazol-2-yl}benzyl)azetidine-3- carboxylic acid 9 ¹H NMR(600 MHz, CD₃OD) δ: 7.93(d, J = 8.2 Hz, 2H), 7.56 (d, J = 8.2 Hz, 2H), 7.43 (d, J = 7.5 Hz, 2H),7.32 (t, J = 7.6 Hz, 2H), 7.23-7.28 (m, J = 7.3 Hz, 1H), 4.87 (m, 1H),4.05 (s, 2H), 3.88 (t, J = 9.0 Hz, 2H), 3.73-3.80 (m, 2H), 3.29-3.36 (m,1H), 2.02-2.19 (m, 2H), 1.30-1.47 (m, 2H), 0.95 (t, J = 7.3 Hz, 3H)

Biological Data

Compounds were synthesized and tested for S1P1 activity using the GTPγ³⁵5 binding assay. These compounds may be assessed for their ability toactivate or block activation of the human S1P1 receptor in cells stablyexpressing the S1P1 receptor.

GTP γ³⁵5 binding was measured in the medium containing (mM) HEPES 25, pH7.4, MgCl₂ 10, NaCl 100, dithitothreitol 0.5, digitonin 0.003%, 0.2 nMGTP γ³⁵S, and 5 μg membrane protein in a volume of 150 μl. Testcompounds were included in the concentration range from 0.08 to 5,000 nMunless indicated otherwise. Membranes were incubated with 100 μM5′-adenylylimmidodiphosphate for 30 min, and subsequently with 10 μM GDPfor 10 min on ice. Drug solutions and membrane were mixed, and thenreactions were initiated by adding GTP γ³⁵5 and continued for 30 min at25° C. Reaction mixtures were filtered over Whatman GF/B filters undervacuum, and washed three times with 3 mL of ice-cold buffer (HEPES 25,pH7.4, MgCl₂ 10 and NaCl 100). Filters were dried and mixed withscintillant, and counted for ³⁵S activity using a β-counter.Agonist-induced GTP γ³⁵5 binding was obtained by subtracting that in theabsence of agonist. Binding data were analyzed using a non-linearregression method. In case of antagonist assay, the reaction mixturecontained 10 nM S1P1 in the presence of test antagonist atconcentrations ranging from 0.08 to 5000 nM.

Table 5 shows activity potency: S1P1 receptor from GTP y³⁵S: nM, (EC₅₀)

TABLE 5 S1P1 IUPAC name EC₅₀ (nM)1-[3-methyl-4-(5-{[1-(3-nitrophenyl)propyl]thio}-1,3,4- 60.9oxadiazol-2-yl)benzyl]azetidine-3-carboxylic acid1-[3-methyl-4-(5-{[1-(3-nitrophenyl)ethyl]thio}-1,3,4- 16.7oxadiazol-2-yl)benzyl]azetidine-3-carboxylic acid1-(4-{5-[(3-chloro-2-fluorobenzyl)thio]-1,3,4-oxadiazol-2- 18.6yl}benzyl)azetidine-3-carboxylic

What is claimed is:
 1. A compound having Formula I, its enantiomers,diastereoisomers, tautomers or a pharmaceutically acceptable saltthereof,

wherein: X is S, SO or SO₂; R¹ is hydrogen, halogen, substituted orunsubstituted C₁₋₃ alkyl, CN, NO₂, C(O)R¹² or OR¹¹; R² is hydrogen,halogen, substituted or unsubstituted C₁₋₃ alkyl, CN, NO₂, C(O)R¹² orOR¹¹; R³ is hydrogen, halogen, substituted or unsubstituted C₁₋₃ alkyl,CN, NO₂, C(O)R¹² or OR¹¹; R⁴ is hydrogen, halogen, substituted orunsubstituted C₁₋₃ alkyl, CN, NO₂, C(O)R¹² or OR¹¹; R⁵ is hydrogen,halogen, substituted or unsubstituted C₁₋₃ alkyl, CN, NO₂, C(O)R¹² orOR¹¹; R⁶ is H, halogen, —OC₁₋₃ alkyl, substituted or unsubstituted C₁₋₃alkyl; R⁷ is hydrogen, halogen, substituted or unsubstituted C₁₋₃ alkyl,CN, NO₂, C(O)R¹² or OR¹¹; R⁸ is CH, S, O, N, NH or CH₂; R⁹ is CH, N orCH₂; R¹⁰ is hydrogen, halogen, substituted or unsubstituted C₁₋₃ alkyl,CN, NO₂, C(O)R¹² or OR¹¹; a is 0 or 1; b is 1, 2 or 3; R¹¹ is H or C₁₋₃alkyl; R¹² is OH or C₁₋₃ alkyl; when a is 1 then

is

when a is 0 then

and R⁸ is S, O, NH or CH₂.
 2. A compound according to claim 1 wherein: Xis S; R⁶ is H or substituted or unsubstituted C₁₋₃ alkyl; a is 1; and


3. A compound according to claim 1 selected from:1-[3-methyl-4-(5-{[1-(3-nitrophenyl)propyl]thio}-1,3,4-oxadiazol-2-yl)benzyl]azetidine-3-carboxylicacid;1-[3-methyl-4-(5-{[1-(3-nitrophenyl)ethyl]thio}-1,3,4-oxadiazol-2-yl)benzyl]azetidine-3-carboxylicacid;1-(4-{5-[(3-chloro-2-fluorobenzyl)sulfanyl]-1,3,4-oxadiazol-2-yl}benzyl)azetidine-3-carboxylicacid; and 1-(4-{5-[(1-Phenylbutyl)sulfanyl]-1,3,4-oxadiazol-2-yl}benzyl)azetidine-3-carboxylic acid.
 4. Apharmaceutical composition comprising as active ingredient atherapeutically effective amount of a compound according to claim 1 anda pharmaceutically acceptable adjuvant, diluents or carrier.
 5. Apharmaceutical composition according to claim 4 wherein the compound isselected from:1-[3-methyl-4-(5-{[1-(3-nitrophenyl)propyl]thio}-1,3,4-oxadiazol-2-yl)benzyl]azetidine-3-carboxylicacid;1-[3-methyl-4-(5-{[1-(3-nitrophenyl)ethyl]thio}-1,3,4-oxadiazol-2-yl)benzyl]azetidine-3-carboxylicacid;1-(4-{5-[(3-chloro-2-fluorobenzyl)sulfanyl]-1,3,4-oxadiazol-2-yl}benzyl)azetidine-3-carboxylicacid; and 1-(4-{5-[(1-Phenylbutyl)sulfanyl]-1,3,4-oxadiazol-2-yl}benzyl)azetidine-3-carboxylic acid.
 6. Amethod of treating a disorder associated with sphingosine-1-phosphatereceptor modulation, which comprises administering to a mammal in needthereof, a pharmaceutical composition comprising a therapeuticallyeffective amount of at least one compound of Formula I

wherein: X is S, SO or SO₂; R¹ is hydrogen, halogen, substituted orunsubstituted C₁₋₃ alkyl, CN, NO₂, C(O)R¹² or OR¹¹; R² is hydrogen,halogen, substituted or unsubstituted C₁₋₃ alkyl, CN, NO₂, C(O)R¹² orOR¹¹; R³ is hydrogen, halogen, substituted or unsubstituted C₁₋₃ alkyl,CN, NO₂, C(O)R¹² or OR¹¹; R⁴ is hydrogen, halogen, substituted orunsubstituted C₁₋₃ alkyl, CN, NO₂, C(O)R¹² or OR¹¹; R⁵ is hydrogen,halogen, substituted or unsubstituted C₁₋₃ alkyl, CN, NO₂, C(O)R¹² orOR¹¹; R⁶ is H, halogen, —OC₁₋₃ alkyl, substituted or unsubstituted C₁₋₃alkyl; R⁷ is hydrogen, halogen, substituted or unsubstituted C₁₋₃ alkyl,CN, NO₂, C(O)R¹² or OR¹¹; R⁸ is CH, S, O, N, NH or CH₂; R⁹ is CH, N orCH₂; R¹⁰ is hydrogen, halogen, substituted or unsubstituted C₁₋₃ alkyl,CN, NO₂, C(O)R¹² or OR¹¹; a is 0 or 1; b is 1, 2 or 3; R¹¹ is H or C₁₋₃alkyl; R¹² is OH or C₁₋₃ alkyl; when a is 1 then

is

when a is 0 then

and R⁸ is S, O, NH or CH₂.
 7. The method of claim 6, wherein thepharmaceutical composition is administered to the mammal to treat oculardiseases, wet and dry age-related macular degeneration, diabeticretinopathy, retinopathy of prematurity, retinal edema, geographicatrophy, glaucomatous optic neuropathy, chorioretinopathy, hypertensiveretinopathy, ocular ischemic syndrome, prevention ofinflammation-induced fibrosis in the back of the eye, various ocularinflammatory diseases including uveitis, scleritis, keratitis, andretinal vasculitis; or systemic vascular barrier related diseases,various inflammatory diseases, including acute lung injury, itsprevention, sepsis, tumor metastasis, atherosclerosis, pulmonary edemas,and ventilation-induced lung injury; or autoimmune diseases andimmunosuppression, rheumatoid arthritis, Crohn's disease, Graves'disease, inflammatory bowel disease, multiple sclerosis, Myastheniagravis, Psoriasis, ulcerative colitis, autoimmune uveitis, renalischemia perfusion injury, contact hypersensitivity, atopic dermititis,and organ transplantation; or allergies and other inflammatory diseases,urticaria, bronchial asthma, and other airway inflammations includingpulmonary emphysema and chronic obstructive pulmonary diseases; orcardiac protection, ischemia reperfusion injury and atherosclerosis; orwound healing such as but not limited to: scar-free healing of woundsfrom cosmetic skin surgery, ocular surgery, GI surgery, general surgery,oral injuries, various mechanical, heat and burn injuries, preventionand treatment of photoaging and skin ageing, and prevention ofradiation-induced injuries; or bone formation, treatment of osteoporosisand various bone fractures including hip and ankles; or anti-nociceptiveactivity, visceral pain, pain associated with diabetic neuropathy,rheumatoid arthritis, chronic knee and joint pain, tendonitis,osteoarthritis, neuropathic pains; or central nervous system neuronalactivity in Alzheimer's disease, age-related neuronal injuries; or organtransplant such as renal, corneal, cardiac or adipose tissue transplant.8. The method of claim 6 wherein the mammal is a human.